12 July 2011

Stylolites in Mississippian limestone

Posted by Callan Bentley

Stylolites (pressure solution seams) in limestone of Mississippian age, exposed on the side of a rounded boulder in Hyalite Canyon, Gallatin Range, Montana. These stylolites, like most, are bedding-parallel, and thus most likely formed due to the weight of the overlying rock. Calcite, the dominant mineral, goes into solution under pressure, and insoluble material, like organic matter and clay, accumulates along the dissolution surface, producing a dark, wiggly line. Here, multiple stylolites have converged and overprinted one another, resulting in a mutli-level “oscilloscope” look.